Thermoforming is a manufacturing process for thermoplastic sheet or film. Specifically, it is more of a converting process, where plastic sheet or film is converted into a formed, finished part. The sheet or film is heated in an oven to its forming temperature, then stretched into or onto a mould and cooled.
Cast or machined aluminum is the most common mould material, although epoxy, wood and structural foam are sometimes used for prototypes, samples, and low volume production runs.
Thermoforming differs from injection molding, blow molding, rotational molding, and other forms of processing plastics, and is primarily used in the manufacture of disposable cups, containers, lids, trays, blisters, clamshells, and other products.